1. Field of the Invention
The present invention relates to fuel rails for fuel-injected internal combustion piston engines, and in particular, to fuel rails for engines having at least one or more banks of cylinders.
2. The Prior Art
Internal combustion piston engines that are fuel-injected typically employ a common pipeline, into which fuel is supplied from the fuel tank, via one or more fuel pumps, and from which fuel is distributed simultaneously to a plurality of fuel injectors for a bank of cylinders. This common pipeline is typically referred to as a common rail or fuel rail.
Such fuel rails are typically formed from cast metal or extruded metal, or in some specialized, less heat sensitive environments, plastic.
In the environment of a V-engine, two fuel rails are typically employed. In a typical prior art environment, two metal fuel rails are provided, one for each bank. From each rail, fittings extend downwardly, that are metal and/or plastic, extending to the individual fuel injectors. Inasmuch as the fuel is usually supplied from the fuel pump into only one of the fuel rails, one or two crossover pipes are provided, that connect the two rails. Usually, barbed fittings are provided at one or both ends of each rail, onto which a rubber, neoprene, or similar material hose is press-fitted, and possibly clamped. An example of such a system is disclosed in Lorraine et al., U.S. Pat. No. 5,511,527. Because many if not most fuel injection systems presently in use are return-type fuel systems, the excess fuel is pumped back to the fuel tank or to a reserve tank, from an outlet from the other of the two fuel rails.
One potential drawback of such a prior art V-engine fuel rail arrangement, is that wicking can occur at the barbed fittings, between the metal and the flexible elastomer hose ends. The amount of fuel that actually escapes is relatively small, and in the past has not significant consequences. However, in view of ever-tightening regulations on not only exhaust emissions, but also on evaporative fuel emissions, such wicking becomes a source of emissions that must be controlled more closely than in the past. In addition, unless the crossover hoses are coated, provided with impermeable inner or outer layers, or otherwise treated with a permeation barrier, the material itself is somewhat porous to fuel, and will out-gas fuel vapor.
All-metal fuel rails, for both in-line and V-engines, are known. However, such fuel rails typically have had relatively rigid constructions, with relatively high tube wall thickness to diameter ratios (e.g., 1:20), particularly in the bends and joints for the crossover pipes for rails for V-engines. As such, installation becomes problematic, often requiring a considerable amount of xe2x80x9cmusclingxe2x80x9d to force the rail into place. This may lead to imposition of bending forces on welded joints that were not intended to resist or withstand such bending forces, or at particular points along long lengths of pipe, rather than distributing the bending forces along the length of a pipe, which could result in kinking or creasing of a pipe at a particular point, creating a weak spot. Alternatively, highly convoluted crossover pipes must be provided, over the lengths of which, the imposed stresses can be distributed.
One additional phenomenon that occurs in fuel rails is that each fuel injector creates pressure pulsations that rebound throughout the length of the rail. A typical fuel injection system operates in the regime of approximately 30 psi to 60 psi. These pressure pulsations can adversely affect the effective operation of the other fuel injectors, to the point that the metering of fuel from the rails into each cylinder can deviate considerably from design specifications. When the fuel metering deviates from the design specifications, this can adversely impact engine performance, fuel economy, and control over exhaust emissions.
One method that has been employed in the past, to address these undesired cross-effects of the fuel pulsations, is to provide accumulator/compensator devices in combination with the fuel rails. Such compensators, which are generally known in the art, may be affixed to the fuel rail, e.g., at positions between adjacent injectors. Alternatively, such devices may be inserted into the interior of the fuel rails themselves. See, e.g., Rohde, U.S. Pat. No. 5,572,262. However, the provision and installation of such compensator devices can considerably increase the cost and complexity of the fuel rail and the entire fuel injection system.
It would be desirable to provide an improved fuel rail construction for use with in-line and V-configuration internal combustion piston engines, that is less likely to contribute to fuel vapor emissions.
It would also be desirable to provide an improved fuel rail construction that is configured to facilitate its installation.
It would further be desirable to provide an improved fuel rail construction that is less susceptible to adverse cross-effects from fuel pulses created in the fuel rail by the injectors, without having to resort to complex dedicated fuel accumulator/compensator devices.
These and other desirable characteristics of the present invention will become apparent in view of the present specification, including claims, and drawings.
The invention comprises, in part, a flexible fuel rail system, for delivery of fuel to the fuel injectors of an internal combustion engine, wherein the internal combustion engine has at least two banks of cylinders. The flexible fuel rail system comprises at least two longitudinal fuel rails, each longitudinal fuel rail being operably configured for delivery of fuel to the injectors for the cylinders of one bank of an internal combustion engine having at least two banks of cylinders. At least one crossover section connects the at least two longitudinal fuel rails in fluid communication with one another. At least one region of enhanced flexibility is in the at least one crossover section. The at least two longitudinal rails, the at least one crossover section and the at least one region of enhanced flexibility are all preferably fabricated from metal material.
Preferably, the at least one region of enhanced flexibility comprises at least one corrugation in the metal material. The at least two longitudinal fuel rails, the at least one crossover section and the at least one region of enhanced flexibility are all preferably monolithically formed from a single piece of metal.
The at least two longitudinal fuel rails preferably each have a substantially non-circular cross-sectional configuration. The at least longitudinal rails each preferably have one of the following cross-sectional configurations: substantially rectangular, substantially oval.
In a preferred embodiment of the invention, at least portions of the sidewalls of the longitudinal fuel rails are operably configured to flex outwardly, in concert with fluctuations in the fuel pressure, in order to provide increased cross-sectional area to at least portions of the longitudinal fuel rails, toward reducing the effects of fuel pressure pulsations created by fuel injectors, upon other ones of fuel injectors in a combustion engine having a fuel injection system.
The present invention also comprises in part a flexible fuel rail system, for delivery of fuel to the fuel injectors of an internal combustion engine, wherein the internal combustion engine has at least one bank of cylinders. The flexible fuel rail system comprises at least one longitudinal fuel rail, each longitudinal fuel rail being operably configured for delivery of fuel to the cylinders of one bank of an internal combustion engine having at least one bank of cylinders. Portions of the sidewalls of the at least one longitudinal fuel rail are operably configured to deform in concert with fluctuations in the fuel pressure, in order to provide variable cross-sectional area to said portions of the at least one longitudinal fuel rail, toward reducing the effects of fuel pressure pulsations created by fuel injectors, upon other ones of fuel injectors in a combustion engine having a fuel injection system.
The at least one longitudinal fuel rail preferably has a substantially non-circular cross-sectional configuration. The at least one longitudinal rail preferably has one of the following cross-sectional configurations: substantially rectangular, substantially oval.
The invention further preferably comprises at least two longitudinal fuel rails, connected by at least one crossover section, the at least one crossover section having at least one region of enhanced flexibility.
Preferably, the at least one region of enhanced flexibility comprises at least one corrugation in the metal material.
Preferably, the at least two longitudinal fuel rails, the at least one crossover section and the at least one region of enhanced flexibility are all monolithically formed from a single piece of metal.